The invention is in a vibration damper having an adjustable damping force.
A vibration damper with adjustable damping force is known from DE 40 31 760 A1, wherein a cylinder which is filled with damping fluid is centered in the container of the vibration damper. An inner container tube is arranged between the container and the cylinder to form a bypass duct to a valve arrangement positioned at the container. The inner container tube has an opening in which a connection piece of the valve arrangement is inserted. The transition between the opening and the connection piece is sealed by a sealing body which is placed on the inner container tube from the outside. The sealing body has seals which are inserted therein and which carry out the actual sealing function.
This solution entails two problems which are solved per se, but only at a relatively high cost. First, the hydraulic pressure in the bypass duct works on the connection piece in the lift off direction so that a correspondingly high pretensioning must be exerted on the seals. Further, a specially three-dimensionally curved seal must be inserted between the sealing body and the outer diameter of the cylinder and a correspondingly adapted sealing body itself must be provided for every variant of the cylinder outer diameter.
DE 44 24 433 C1 is directed to an intermediate tube for a vibration damper with adjustable damping force comprising a tube connection piece which has a covering with a valve seat body and forms a hydraulic connection with a controllable valve. Clamped within the tube connection piece is an intermediate ring which, in practice, lengthens the tube connection piece. In comparison to the proposal according to DE 40 31 760 A1, this solution offers the advantage that the opening in which the intermediate ring is clamped can be maintained constant substantially independent from the diameter of the intermediate tube, so that there is an appreciable standardizing effect. However, the materials which are necessary for the clamping action are mostly composed of plastic and are thus relatively sensitive to pressure and temperature.
German Utility Model DE-GM 92 06 568 U1 discloses an intermediate tube with a connection piece which is drawn from the intermediate tube so as to form one piece therewith. In the particular case of longer tube connection piece lengths, a radius is formed at the intermediate tube which provides a transition between the intermediate tube portion and the tube connection piece. In this solution, the flowability of the material imposes limits with respect to the forming of the tube connection piece. Further, a minimum wall thickness must be maintained so that the tube and connection piece can withstand the operating pressures which develop.
DE 44 10 522 A1 shows a hydraulic vibration damper with a jacket tube having a welded in tube connection piece within a collar of the jacket tube. In principle, the welding seam between the tube connection piece and the collar of the jacket tube is checked by means of a pressure test. Moreover, a working step is generally required for cleaning the jacket tube after the welding process.
A different approach is disclosed in DE 41 14 307 A1. A connection face for the tube connection piece is formed integral with the jacket tube in a planar manner, an adjustable bypass valve being welded onto this jacket tube. The tube connection piece is then placed on the plane connection face from the outside for the welding process, wherein the necessary welding seam lies in a plane and is not three-dimensionally curved.
The object of the present invention is to so develop a vibration damper with a shut-off valve arrangement arranged at the container tube such that even high operating pressures and temperatures can be maintained under control while allowing for a standardized application of the invention.